4 Things You Absolutely Need to Know Before Buying Olive Oil

4 Things You Absolutely Need to Know Before Buying Olive Oil

*This is a guest post from Jonathan Carp, MD, drcarp.com.

Olive Oil is one of the most common oils used by health enthusiasts. I have a friend who is an olive oil judge and he tours the world, going to olive oil competitions in Spain. And he is able to taste the rancidity or the oxidation of an olive oil. He tells me that majority of the oils out there are rancid. We can’t really taste them, but he can.

The fact is most olive oils on the shelf are rancid. Chances are, that olive oil you’ve been putting on your salad or using for cooking is rancid.

  1. Why Your Olive Oil Might Be Rancid

Four factors cause rancidity in olive oil:

  1. Light
  2. Heat
  3. Mixed Oils
  4. Air

Exposure to sun and excessive heat cause rancidity. That’s why you need to look for an amber-colored or a non-transparent bottle. If the bottle is clear, I absolutely wouldn’t buy it. You also need to make sure that it’s a glass container because glass is the most inert chemical and as such, it will not react with the olive oil.

Another thing you need to consider is if it has other oils mixed with it. When you look at the back, it will have a bunch of abbreviations like ES for Spain or GR for Greece. But when you see mixed oils all coming into one vat, that means the product went through so much mixing, exposing it to too much air. Too much air causes rancidity in olive oil.

  1. Time of Harvest Affects Olive Oil Quality and Shelf Life

Some European countries have been growing olives for a long time. When they harvest the olive very, very early in the season, they don’t get that much oil though. But what’s interesting here is the olive in the very beginning of the season has much more polyphenols in it, which prolong the shelf life of the olive oil.

It’s hard to know if the farmer waits until the end of the season where the polyphenols are low, but the yields are high before harvesting olives. One way to check out the quality of your olive oil is through an association in California called the California Olive Oil Council (COOC).

COOC assesses olive oils and certifies if the olive oil “meets both chemical and sensory standards to be sold as extra virgin.” Any olive oil that has the COOC seal is okay to purchase, especially if you are consuming olive oil regularly.

  1. How Much Olive Oil You Consume Matters

When people are on an autoimmune diet that I prescribe to my patients, I have them eat no more than 3 to 4 tablespoons of olive oil per day. That’s because it has a lot of calories. Olive oil has 120 calories per tablespoon. If you’re pouring olive oil all over your salad, you’re getting a lot of calories. Generally speaking, they’re good calories, but in the beginning of the diet and getting your health in order, we need to pay attention to the amount of calories you take in.

When it comes to cooking, you can cook with olive oil using medium to high heat.

  1. Light Olive Oil vs Regular Olive Oil

Light olive oil goes through a secondary process to make it lighter. Anytime it goes through any form of secondary process, especially with an extra virgin oil, then it’s going to be exposed to more light and there would be an increased risk for rancidity.
There’s no point in getting a light olive oil version. Olive oil is an important part of a healthy diet, but people use too much of it and they’re not getting quality olive oil.

The fact that people might be consuming olive oil that is rancid is a cause for alarm. You have to realize that you’re actually using up antioxidants to counteract the damaging effects of eating oxidized food. When you’re ingesting oxidized food, your body needs antioxidants to counteract that. It would be a waste to let those antioxidants go to counteracting the damaging effects of the rancid oil instead of letting your body use it for improving your health.

I hope I answered your questions about olive oil. If you have more questions or comments, please comment below. You can also post your questions and join the conversation on our Weight Loss Awakening Friendship Facebook Group.

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David – do not use Olive Oil in a fryer, it is not an oil that is meant for that and will be damaged by the heat. But for general use, my friend who is an Olive Oil judge says the Costco brand is actually pretty high in quality. I would avoid deep frying anything, if you can, it might taste good but it’s really bad for you.


Just curious which olive oil you recommend, I currenly use the costco organic brand. Also, is it ok to use olive oil in my deep fryer?

david roberts

Barbara, COOC only does California. Yes, they have a system of testing. Yes, many do press dates. I like California Ranch as it is readily available but COOC has lots of suggestions


I only buy olive oil from california grown ones. The European ones are controlled by the mafia and diluted and God knows what else.

Shahla esfandiary

The COOC, does it test all oils or just Calif. Do any oils date the bottling time? That would help.


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